1. Field of the Invention
The present invention relates to a laser irradiation apparatus and method of fabricating an organic light emitting display using the same and, more particularly, to a laser irradiation apparatus including a mask in which a length of a middle portion of a mask pattern is patterned to be longer than those of an upper portion and a lower portion of the mask pattern on the basis of a scanning direction, and method of fabricating an organic light emitting display using the same
2. Description of the Related Art
In general, an organic light emitting display, which is a flat panel display, includes an anode, a cathode, and organic layers between the anode and the cathode. The organic layers include at least an emission layer. The organic layers may further include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer, in addition to the emission layer. The organic light emitting display may be classified into a polymer organic light emitting display and a small molecule organic light emitting display depending on the organic layer, particularly, a material that forms the emission layer.
In order to realize a full color organic light emitting display, it is required to pattern the emission layer. A method of patterning the emission layer includes a method using a shadow mask in the small molecule organic light emitting display, and an ink-jet printing method or a laser induced thermal imaging (hereinafter, referred to as LITI) method in the polymer organic light emitting display. With the LITI method, it is possible to finely pattern the organic layer. The LITI method is usable for a large-sized display and is advantageous in high resolution. Advantageously, the LITI method is a dry process, unlike the ink-jet printing that is a wet process.
FIG. 1 is a cross-sectional view illustrating a method of forming an organic layer pattern using an LITI method.
Referring to FIG. 1, a donor substrate 120 where an organic layer 130 is formed is laminated on a substrate 110 where a predetermined element is formed. When a laser beam 150 is irradiated on a predetermined region of the donor substrate 120 having the organic layer 130, the laser beam 150 is absorbed by a light-to-heat conversion layer of the donor substrate 120 and then converted to thermal energy, which allows the organic layer 130 forming a transfer layer to be transferred onto the substrate 110, thus patterning the organic layer on the substrate 110. In this case, the organic layer 130 is separated from the donor substrate 120 by the thermal energy, and is transferred onto the substrate 110 while bonding within the organic layer 130 is broken. Energy required to break the bonding within the organic layer 130 should be higher than energy required to allow the organic layer 130 to be broken from the donor substrate 120 and transferred. Dotted portions indicate portions where the bonds within the organic layer 130 are broken.
FIGS. 2A to 2C are schematic views illustrating a method of fabricating an organic light emitting display using a conventional laser irradiation apparatus.
Referring to FIG. 2A, a donor substrate 120 where an organic layer 130 is formed is laminated on a substrate 110 where a pixel electrode is formed.
The laser irradiation apparatus 200 includes a laser generator 240, a patterned mask 260, and a projection lens 270. The laser generator 240 irradiates a laser beam 250 on a predetermined region of the donor substrate 120, and performs scanning in an arrow direction. In this case, the laser beam 250 irradiated from the laser generator 240 penetrates the patterned mask 260, and the penetrated laser beam 250 is focused by the projection lens 270 and then irradiated on the donor substrate 120. The laser beam 250 is shielded from a portion where the mask 260 is not patterned.
Referring to FIG. 2B, the laser beam 250 performs scanning on the donor substrate 120 including a region where the pixel electrode 210 is formed. An oblique line portion indicates a region 255 on which the laser beam 250 performs scanning.
By means of the scanning of the laser beam 250, the organic layer 130 on the donor substrate 120 is transferred onto the substrate 110 where the pixel electrode 210 is formed. After the transfer process, a cathode is formed on the organic layer pattern, thereby completing the fabrication of the organic light emitting display.
Referring to FIG. 2C, the amount of laser irradiated on a scanning region while the laser beam is scanned is shown as a beam profile 280 of the laser beam 250 irradiated on the donor substrate 120. An x-axis indicates a region where the laser beam is scanned and a y-axis indicates energy of the laser beam. In particular, the amount of the laser beam irradiated on the scanning region of the donor substrate 120 is uniform. That is, it can be seen that the laser beam is uniformly irradiated over the entire region of the donor substrate 120 where the laser beam is irradiated. As shown in FIG. 1, energy required to break the bonding within the organic layer 130 should be higher than that required for allowing the organic layer 130 to be separated from the donor substrate 120 and transferred. As a result, energy required for breaking the bonding within the organic layer 130 is applied in order to transfer the organic layer 130. That is, an excessive amount of energy may be applied to transfer the organic layer 130, which may cause the organic layer to be damaged and the quality of the transferred organic layer pattern to be degraded.